All chromosome number information was obtained from McArthur and Sanderson (1999) as updated in McArthur (2005). Appendix 1 contains a general summary of characteristics useful to separate subspecies. See McArthur and Stevens (2004) for a detailed review of the characters for the subspecies occurring in the Intermountain West.

Basin big sagebrush usually occurs at the lowest elevational range of the species, being most abundant in the valley bottoms to mountain foothills. Plants typically have a single main trunk and may grow to a height of 4 m (13 ft) under proper conditions, making basin the largest subspecies. Basin big sagebrush plants are generally uneven-topped with loosely branching flowering stems distributed throughout the crown (see figure 1). Floral heads typically contain 3 to 6 small flowers per head. Leaves of the vegetative stems are narrowly cuneate averaging 2 cm (0.8 in) or more and can be as long as 5 cm (2 in) being many times longer than wide (see figure 2). Ultraviolet visible coumarins in leaf extracts are minimal; leaf UV color is none to light blue in water and a rusty red-brown color in alcohol. 2n = 18 or sometimes 36.

Figure 3. Wyoming big sagebrush.

Derek Tilley, USDA NRCS Idaho PMC

Wyoming big sagebrush overlaps in range and elevation with basin big sagebrush. Plants are considerably smaller than those of basin big sagebrush, usually less than 0.9 m (3 ft) tall, and have main stems branching from the ground (see figure 3). Flowering stems are not as widely branching as those of basin, but otherwise closely resemble that subspecies. Leaves are typically shorter, from 1 to 1.5 cm (0.4 to 0.6 in) long, and flabelliform. UV extract color in water is none to light blue and rusty in alcohol. 2n = 36.

The vegetative stems of mountain big sagebrush create a characteristic even topped crown with the panicles rising distinctly and relatively uniformly above the foliage (see figure 3). Plants are normally smaller than those of basin big sagebrush, averaging about 0.9 m (3 ft) tall. Inflorescences are narrow and spicate bearing flower heads containing 4 to 8 flowers per head. Leaves are characteristically wider than those of basin or Wyoming big sagebrush. In extracts, ultraviolet visible coumarins are abundant. Leaf extracts fluoresce blue in water and blue-cream in alcohol. 2n = 18 or sometimes 36.

Figure 4. Even topped mountain big sagebrush.

Derek Tilley, USDA NRCS Idaho PMC

Originally considered a xeric form of mountain big sagebrush, xeric big sagebrush shares similarities with both basin and mountain big sagebrush and may be the result of hybridization between the two subspecies. Xeric big sagebrush plants are large and have an uneven topped crown like those of basin big sagebrush, but in leaf UV color and cytological characters it resembles mountain big sagebrush. Ultraviolet visible coumarins are blue in water, blue-cream in alcohol. 2n = 36.

A new variation of big sagebrush being recognized by some is Bonneville big sagebrush. This as yet undescribed taxon may represent hybridization between Wyoming and mountain big sagebrush. It is reported to have the general growth form of Wyoming plants but bears the leaves and fluorescing characteristics of the mountain subspecies. It has been reported from the bench areas of Lake Bonneville and other ancient lakes of the Intermountain West in Utah and Nevada. Reports of Bonneville big sagebrush have also come from western Wyoming and western Colorado. Of particular importance is this sagebrush’s reported high palatability to wild ungulates and sage grouse.

Subalpine, or spicate big sagebrush, is believed to be a stabilized hybrid between mountain big sagebrush and silver sagebrush (Artemisia cana Pursh ssp. viscidula [Osterhout] Beetle). Plants are similar to those of mountain big sagebrush except that leaves and floral heads are larger, the floral heads having 10 to 18 flowers per head. Ultraviolet visible coumarins in leaf extracts fluoresce blue in water and blue-cream in alcohol. 2n = 18 or 36.

Parish’s big sagebrush is an uncommon taxon restricted to dry, sandy soils in the hills of southern California. It is nearest in appearance and relationship to basin big sagebrush, but differs from basin in having drooping flowering branches and the achenes are hairy. 2n = 36.

One additional taxon that should be mentioned is Lahontan sagebrush (Artemisia arbuscula ssp. longicaulis Winward and McArthur). It is thought to be a stable hybrid between low sagebrush (A. arbuscula) and Wyoming big sagebrush. It bears the flowers of low sagebrush but has the vegetative characteristics of its big sagebrush parent. This subspecies forms dominant communities in northwestern Nevada and adjacent portions of California and Oregon in shallow or clayey soils above and around the shoreline of the Pleistocene Lake Lahontan.

The following key should provide some assistance in separating the subspecies of big sagebrush.

1. plants larger, usually >0.9 m (3 ft) tall, with a

single main trunk; crown uneven with floral stems

throughout

2. achenes hairy; floral stems drooping; plants

endemic to sandy soils in southern

California……………………......ssp. parishii

2. achenes glabrous; floral stems erect; plants

widely distributed throughout western U.S,

including southern California

3. plants occurring in valley bottoms and low

foothills, occupying deep fertile soils; leaves

narrowly cuneate, 2-5 cm (0.8-2.0 in) long,

UV leaf color in water=none, in alcohol=red

to brown ……...................…...ssp. tridentata

3. UV in water=blue, in alcohol=blue-cream;

plants restricted to well-drained basaltic soils in western Idaho….........ssp. xericensis

1. plants smaller, averaging 0.9 m (3 ft) or less, with

trunks branching at or near ground level; crowns

various

4. crowns uneven-topped, plants of low

valleys and foothills;

5. UV color in water=none, in alcohol=rust

…………………………..ssp. wyomingensis

5. UV color in water=blue, in alcohol=blue-

cream…………………………..(Bonneville)

4. crowns even-topped, floral stems rising

uniformly above the vegetative stems; plants of

higher elevations

6. flowers 4 to 8; leaf tips lobed

………………………………….ssp. vaseyana

6. flowers 10 to 18; leaf tips often pointed

……….…………...…………..ssp. spiciformis

Additional taxonomic information can be found in the Flora of North America, Volume 19 (FNA Editorial Committee 2006) and the Intermountain Flora, Volume 5 (Cronquist et al. 1994).

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Description

General: Although big sagebrush plants generally have a similar growth form, the species does have considerable morphological variation with several subspecies and ecotypes. Big sagebrush are evergreen shrubs ranging in size from less than 0.6 m (2 ft) tall to as large as 4 m (13 ft) tall. Branches are spreading, arising from numerous main stems in the lower growing subspecies or from one main trunk in the larger forms. Leaves are blue-gray to blue-green in color due to dense gray hairs. They are typically cuneate (wedge-shaped, triangular and gradually tapering to the base) or flabelliform (bell shaped) depending on subspecies, and have three lobes at the apex on the majority of the persistent foliage. Leaves vary in length from 0.5 to 5 cm (0.2 to 2.0 in), and can be 0.2 to 2.0 cm (0.08 to 0.8 in) wide. Leaves are spirally arranged with internodes short in young vegetative stems making the leaves very dense. Panicles overtop plants of mountain and spicate big sagebrush, or can grow throughout the crown in basin and Wyoming big sagebrush. Floral heads contain from three to 18 perfect (both male and female parts present) flowers per head. Achenes are typically glabrous but are hairy in the California endemic Parish’s big sagebrush. Big sagebrush plants are very aromatic with the smell being described as bitter pungent to pleasant, the odor varying by subspecies. Ploidy levels often differ among subspecies and may differ among populations.

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Wyoming big sagebrush occurs from Montana and North Dakota south to California, New Mexico, Colorado, and Nebraska [64,133,144]. Its population distribution is poorly understood in areas where it overlaps with other big sagebrush subspecies [139,144].

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Fossil records and records from early pioneers indicate that sagebrush was widespread and existed in nearly the same general distribution for the past several thousand years as it does in the present day. Densities of sagebrush communities, however, have been reduced historically due to range management practices. Big sagebrush presently covers a vast ecological range from British Columbia to Baja California eastward to the Dakotas. Mahalovich and McArthur (2004) provide distribution as well as seed and plant transfer guidelines for Artemisia subgenus Tridentatae. For current distribution for each subspecies, please consult the Plant Profile page for this species on the PLANTS Web site.

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Physical Description

Morphology

Description

Wyoming big sagebrush is a native shrub [6,34,39,64]. It is the most drought tolerant of the 3 major big sagebrush subspecies [94]. Plants are generally 18 to 30 inches (46-76 cm) tall, with rounded, uneven crowns. The main stem is usually branched at or near ground level into 2 or more substems [11,112]. Wyoming big sagebrush is technically an evergreen but is semideciduous in habit. It develops 2 types of leaves: large ephemeral leaves and smaller, perennial leaves produced from ephemeral leaf axes [96]. The inflorescence is an open, many-flowered spike [11]. The fruit is a small, easily shattered cypsela [116].

The root system is deep and well developed, with many laterals and one or more taproots. The majority of roots (about 35% of the total root system) are in the upper 1 foot (30.5 cm) of soil. Some roots may penetrate as far as 6 feet (1.8 m) [51,85,124]. Roots are infected with the vesicular-arbuscular mycorrhizae (VAM) Glomus microcarpus and Gigaspora spp. [16,36,71].

Wyoming big sagebrush is a long-lived species. In an undisturbed Wyoming big sagebrush community in southern Wyoming, plants ranged from 26 to 57 years of age; average age was 42 years [124]. Plants in long-undisturbed communities of New Mexico typically reach 50 years of age [135]. Maximum life span may exceed 150 years [50].

Identification of big sagebrush subspecies based upon morphology is difficult and often faulty. This is especially true for Wyoming big sagebrush, which is intermediate in several characteristics used to distinguish basin and mountain big sagebrush [67,129,132,139,149]. Chemical analyses are more reliable, but they cannot be conducted in the field and sometimes give indeterminate results [140]. Combining field identification with chemical analysis produces the most positive identification of subspecies. Laboratory techniques used to identify Wyoming and other big sagebrush subspecies include paper chromatography [78,115], UV absorption [120,121], and DNA analysis [89].

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Ecology

Habitat

Comments: Rocky or fine-grained soils, cold-desert basins to high plateaus, foothills; 800-2200 m. Subspecies tridentata is the common sagebrush of deep, well-drained soils in the Great Basin of western North America, where it is often the dominant shrub of valleys and open grasslands. On drier sites and on high plateaus, it is replaced by subsp. wyomingensis, a taxon that appears to be increasing with prolonged droughts and disturbance from grazing.

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Habitat characteristics

Wyoming big sagebrush is most common on foothills, undulating terraces, slopes, and plateaus, but also occurs in basins and valley bottoms [34,39,54,69,128]. Aspect varies, but shrubs are most common on south- to west-facing slopes [28,128,131].

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Key Plant Community Associations

Wyoming big sagebrush steppe communities are prevalent in the West. Wyoming big sagebrush/bluebunch wheatgrass (Pseudoroegneria spicata) is the most common of the big sagebrush/bluebunch wheatgrass types [95]. Other codominants in Wyoming big sagebrush steppe include western wheatgrass (Pascopyrum smithii), Sandberg bluegrass (Poa secunda), bottlebrush squirreltail (Elymus elymoides), Idaho fescue (Festuca idahoensis), Thurber needlegrass (Achnatherum thurberianum), and needle-and-thread grass (Hesperostipa comata) [37,54,67,86]. Although not often used in vegetation classifications, cheatgrass (Bromus tectorum) is also a dominant species in some Wyoming big sagebrush steppe communities [37]. Evenden [46] described a Wyoming big sagebrush/cheatgrass community in the Trout Creek Mountains of southeastern Oregon where Wyoming big sagebrush and cheatgrass comprised 40 and 28% cover, respectively.

Wyoming big sagebrush occurs in pinyon-juniper (Pinus-Juniperus spp.) woodlands and ponderosa pine (P. ponderosa) forests, often as a dominant shrub [42,109,127,147]. It is the most abundant big sagebrush subspecies in singleleaf pinyon(P. monophylla)-Utah juniper (J. osteosperma) communities of northern Arizona [69]. It is also common in singleleaf pinyon-Utah juniper communities of the northern Great Basin [147].

Species diversity is lower in Wyoming big sagebrush communities than in other big sagebrush types. A few perennial forb species are usually present in low numbers [27]. Common associates of Wyoming big sagebrush are listed below by state.

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The big sagebrush complex is adapted to a wide range of precipitation zones and soil conditions. Plants are well adapted to the arid plains, valleys, foothills and mountains of the West where annual precipitation ranges from as little as 200 to as much as 750 or more mm (8 to 30 in). It is often found growing in loamy to sandy loam soils, but plants are found on all 12 soil textural classes in five soil orders: Alfisols, Aridisols, Entisols, Inceptisols and Mollisols. Tolerance to alkalinity or acidity varies by subspecies. In general big sagebrush will grow in soils with a pH of 5.9 to 10.0 and with organic matter content of 0.62 to 4.14 percent.

Basin big sagebrush is commonly found at low to mid elevations from 600 to 2,100 m (1,900 to 6,900 ft) in valleys and mountain foothills, occupying sites with deep fertile loamy to sandy soil, 0.9 m (3 ft) or deeper. It is often the dominant shrub species of the plant community, but is also found in association with juniper, piñon pine and rabbitbrush communities. Basin big sagebrush has a deep penetrating root system that allows it to occupy deeper soils in areas receiving little precipitation. Plants are often found growing in valleys, plains, alluvial fans and in seasonal or perennial stream channels. Basin big sagebrush prefers soils which are non-alkaline, non-saline and non-calcareous. The deep root system does not allow plants to grow in soils with a soil depth limiting hardpan or caliche layer. Depending on soil infiltration and water storage capacity, plants will grow in areas receiving less than 200 to more than 400 mm (8 to 16 in) annual precipitation. This subspecies also does not tolerate soils saturated for more than a few weeks in a season.

Wyoming big sagebrush grows at low to intermediate elevations between basin and mountain big sagebrush, but also commonly overlaps in range with the other two subspecies. When found in proximity with basin big sagebrush, Wyoming sagebrush will occupy the shallower, better-drained soils. Like basin big sagebrush, Wyoming is typically found in large stands covering many acres. Plants are also found in juniper, rabbitbrush, bitterbrush and mountain mahogany communities. At lower precipitation areas it is sometimes intermixed with shadscale and other Atriplex species. Wyoming big sagebrush commonly occurs from 800 to 2,200 m (2600 to 7,200 ft) in elevation. Wyoming big sagebrush is the most drought tolerant of the big sagebrush subspecies and is commonly found growing on low valley slopes and foothills receiving between 200 and 300 mm (8 to 12 in) annual precipitation. It occupies loamy soils with high clay content and a depth of 25 to 75 cm (10 to 30 in). Soils may be quite rocky or gravelly, but in these cases plants will be smaller. Wyoming big sagebrush will be found growing in soils underlain by a caliche or silica layer if the available soil is deep enough. Plants are typically found in soils with a low water holding capacity where excess water may run off into channels more suitable to basin big sagebrush.

Xeric big sagebrush is limited to basaltic and granitic soils of western and west central Idaho and is often associated with bluebunch wheatgrass. Plants grow in the foothills from 800 to 1,500 meters (2,600 to 4,900 ft). Precipitation ranges from 300 to 400 mm (12 to 16 in) annually.

Spicate big sagebrush grows at high elevation ridge lines and snow accumulation areas from 2,000 to 3,300 m (6,500 to 10,800 ft) in annual precipitation zones of over 750 mm (30 in). It is normally found near Douglas fir, spruce-fir, and aspen communities.

Parish’s big sagebrush is adapted to the dry sandy soils of California’s Inner South Coast Ranges, South Coast, Western Transverse Ranges, White and Inyo Mountains and the desert mountains of the Mojave Desert.

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Dispersal

Establishment

Seed of big sagebrush are best adapted to germinate in habitats with ecological conditions approximating those of the seed collection site. Seed source and subspecies should always be seriously considered prior to seeding. It may be necessary to use seed from more than one subspecies in a given revegetation project to ensure adequate establishment in all habitats.

Seed should be sown in the late fall or early winter and allowed to naturally stratify. It should be noted that big sagebrush seed has special seed storage requirements (See “Seed and Plant Production” section). If stored in conditions with relative humidity above 30 percent, seeds lose vigor and germinability after two or three years. To ensure a greater chance of establishment success, check the viability of seed lots before planting.

Seed should be planted into a firm, weed-free seedbed at a depth of no more than 1/8 inch. Seed covered too deeply with soil will generally fail to establish. Best results come from surface broadcast seed that has been pressed into the soil to provide for good seed-soil contact. Seed can also be broadcast directly onto snow with good results. Pressing broadcast seed into the soil surface with a land imprinter has provided very good establishment success. Land imprinters create good contact between the seed and soil as well as provide microhabitats that optimize temperature and water requirements. Broadcast seeding has also yielded good results when followed by a cultipacker or drag chain.

Drill seeding can be successful, but strict attention must be paid to seeding depth. Optimal drilling depth is 0 to 1/8 inch.

Sagebrush seed lots range in purity from approximately 8 to 30 percent or greater pure seed. Seed lots with high purity levels (20 percent or greater) can be difficult to seed due to limitations of the seeding equipment. Because sagebrush seed is very small and is metered through seeding equipment with difficulty, seed can be diluted with rice hulls or another inert carrier to improve flow.

Post-fire aerial seeding of big sagebrush has been done with limited success. Studies suggest that best results come from aerial seeding followed by land imprinting, cultipacking or chaining, or after allowing native perennial grasses to establish for a season following fire. It is believed that native grasses would suppress exotic annual grass species while allowing the establishment of sagebrush. Further study of this option is indicated.

Big sagebrush is not recommended for pure seedings. Seed should be a small component of a seed mix. Drill seeding 0.025 lbs PLS per acre (approximately 1 viable seed/ft²) provides approximately 400 plants per acre for optimal wildlife habitat. For broadcast seeding increase to 0.05 to 0.075 lbs PLS (approximately 2-3 viable seeds/ft²). With adequate soil moisture seedlings develop quickly and compete well with other shrubs and most herbaceous plants. However, to enhance establishment, sagebrush should not be sown in the same drill row with more aggressive forbs and grasses.

Sagebrush seedlings require sufficient soil moisture to germinate and survive. Young plants do not do well in open, unprotected locations. Best establishment results occur in sites where soil moisture is at or near field capacity, or in areas where snow accumulates. Existing shrubs, downed trees and litter can create microhabitats which also provide very good germination conditions.

Containerized stock or bareroot seedlings can also be used with high establishment success (50% or greater). This method, however, is quite costly, and is rarely used except in small critical area plantings. Plants can be taken from nursery stock or field harvested wildings. Wildings should be collected and transplanted during dormancy in fall or very early spring when soil moisture conditions are best. For best cost efficiency, “mother plants” should be placed in key locations throughout the revegetation site to allow for natural seed dispersal and recruitment over time.

Fire Management Considerations

Burning is the oldest method of big sagebrush control in the West, and it is still effective and relatively inexpensive. Sites generally need reburning every 15 to 30 years in order to control big sagebrush [85,112]. Composition of herbaceous vegetation is largely unaffected by burning, whereas herbicide control may reduce herb production by 45 to 65% [4,85]. Unlike burning in other big sagebrush types, burning in Wyoming big sagebrush usually does not usually increase forb density or diversity [53,58,151].

Fuels and Fire Guidelines: Prescribed burning may be difficult on some sites due to low fuel loads, but under the right combination of wind and high temperature, sparsely fueled Wyoming big sagebrush communities can burn [150]. On Wyoming big sagebrush rangeland in southern Idaho, prescribed burning in April, when fine fuels left over from the prior growing season carry a relatively "cool" fire, has been successful. Autenhreith and others [4] recommend burning in strips of not more than 50 yards (45 m) wide and 100 yards (90 m) in length in order to preserve some big sagebrush for wildlife. They do not recommend winter burning in sage grouse habitat, as winter availability of sagebrush is crucial to the birds.

Frandsen [55] developed a model estimating fuel load of Wyoming big sagebrush for fire behavior predictions. Britton and others [24] present a big sagebrush canopy cover-herbaceous fuel load curve representing proportions of big sagebrush cover and herbaceous fuels needed to produce a successful burn. Brown [25] has developed a model for fuel and fire behavior prediction in Wyoming and mountain big sagebrush based on sampling in Montana and Idaho.

General guidelines for burning big sagebrush types: For stand-replacing fire, Beardall and Sylvester [9] recommend fine fuels of 600 to 700 lbs/acre (674-786 kg/ha). Big sagebrush should be at least 1/3rd of total plant cover [104].

Postfire Management: Native species that have been successfully seeded in after fire on degraded Wyoming big sagebrush rangelands include bluebunch wheatgrass, fourwing saltbush (Atriplex canescens), scarlet globemallow (Sphaeralcea coccinea), and balsamroot (Balsamorhiza spp.). Russian wildrye (Psathyrostachys juncea), crested, and desert wheatgrasses have also been successfully seeded in [80,150]. Reoccupation of Wyoming big sagebrush is slower on sites seeded to crested or desert wheatgrass than on sites seeded to native grasses [112].

Deferment of grazing is recommended for 1 to 2 years after burning Wyoming big sagebrush/grass types to allow native grasses to recover [69,104,152].

Cheatgrass: While burning will remove Wyoming big sagebrush, it will not restore perennial grasses in areas where cheatgrass has become dominant [27]. Arid regions may be most susceptible to cheatgrass invasion. Hironaka and others [67] reported that in the Wyoming big sagebrush/bluebunch wheatgrass type, cheatgrass has been less invasive in eastern Idaho than in the drier regions of southern Idaho, eastern Oregon, and northern Nevada and Utah. To reduce cheatgrass invasion after burning, they recommend a gradual reduction in shrub cover so that bluebunch wheatgrass and other bunchgrasses regain vigor and produce a continuous supply of seed.

In general, burning in cheatgrass-infested big sagebrush types is not recommended if cheatgrass cover exceeds 50% or if cover of fire-resistant native grasses is less than 20%. Cheatgrass is more likely to invade after fire if the dominant native grass is not a fire-resistant species (for example, Thurber needlegrass or Idaho fescue) or if native grasses were in poor condition prior to fire [104,146]. Artificial seeding with native grasses is recommended after fire if cheatgrass was a major component of the prefire community or if it was a minor component and native grasses were in poor condition [146,155].

Communities in good condition may at least partially recover from temporary postfire increases in cheatgrass, especially when fire is followed by favorable precipitation. For example, a summer wildfire in central Utah occurred in a Wyoming big sagebrush/bluebunch wheatgrass community in good condition shortly after vegetation sampling was performed for a different study. Precipitation was above average in postfire years 1 and 2. Further vegetation sampling was done in postfire years 1 and 2 for a fire effects study. Wyoming big sagebrush was removed by fire. Bluebunch wheatgrass recovered quickly, almost equaling prefire coverage by postfire year 2. Cheatgrass coverage increased greatly on both burned and unburned control plots, with coverage on burned plots over twice that on unburned plots. The authors concluded that on this rangeland, postfire seeding would not have increased abundance of bluebunch wheatgrass and other native grasses relative to cheatgrass. Pre- and postfire coverages of Wyoming big sagebrush, bluebunch wheatgrass, and cheatgrass are given below. Data are means and 1 standard error [146]. ----------------Burned---------------- Prefire Postfire yr 1 Postfire yr 2 sagebrush 6.5(1.3) 0 0 wheatgrass 12.9(5.0) 6.5(1.7) 12.3(4.9) cheatgrass 6.6(1.5) 34.8(12.1) 56.8(5.4) ------------Unburned Control---------- Prefire Postfire yr 1 Postfire yr 2 sagebrush 2.3(1.2) 3.7(1.2) 5.7(4.0) wheatgrass 13.3(0.5) 16.0(1.) 13.3(5.9) cheatgrass 6.8(1.1) 11.0(1.1) 24.0(8.2) Restoration of cheatgrass-dominated sites: Boltz [18] found seed imprinting resulted in best establishment of Wyoming big sagebrush seedlings the Jarbidge Resource Area of south-central Idaho. He studied natural and artificial regeneration on sites that had been subject to repeat wildfire and cheatgrass invasion. Natural regeneration of Wyoming big sagebrush was poor on cheatgrass-overrun sites receiving less than 10 inches (254 mm) average annual precipitation. He speculated a depleted seedbank combined with low and erratic precipitation resulted in low Wyoming big sagebrush seedling density and high seedling mortality. Imprinting seed into the soil after May prescribed burning on an already thrice-burned site in poor condition resulted in Wyoming big sagebrush establishment at an average rate of 2,750 seedlings/acre (6875/ha). Among imprinting, broadcasting, drilling, disking, or chaining seed, broadcasting was 2nd most successful at 750 seedlings/acre (300/ha).

Cheatgrass is most likely to invade the Wyoming big sagebrush/Thurber needlegrass type if overgrazing has preceded fire. Hironaka and others [67] suggest that due to low seedling vigor of Thurber needlegrass, restoring this type after cheatgrass becomes dominant would be difficult to impossible. They recommend artificial seeding with desert wheatgrass.

When perennial herbs are depleted by overgrazing or other means, the Wyoming big sagebrush/needle-and-thread grass type is easily invaded by cheatgrass because it tends to occur on warm soils. However, needle-and-thread grass is easier to establish by artificial seeding than most native bunchgrasses. Hironaka and others [67] recommend direct-seed drilling needle-and-thread grass into nontilled soil when cheatgrass has invaded this type.

Other invasive species: Rabbitbrush (Chrysothamnus spp.) may invade burned sites in the northern Great Basin. Rabbitbrush invasion after fire has occurred most often in western Idaho, and is least likely in eastern Idaho and Wyoming [27].

Sage grouse: Fire is an effective tool for promoting sage grouse [14,58,82,114]. For information on fire management of sage grouse habitat, see the FEIS report on sage grouse (Centrocercus urophasianus).

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Broad-scale Impacts of Plant Response to Fire

Prescribed burning in Wyoming big sagebrush has been accomplished on patches as little as 0.3 acre (0.05 ha) [105] and as much as 14,500 acres (5800 ha). The 14,500-acre fire, on the Upper Snake River Plain of Idaho, burned about 57% of the area and reduced Wyoming big sagebrush and threetip sagebrush (Artemisia tripartita) cover from approximately 20 to 11% [53]. The small patchy fires, on the East Fork of the Salmon River in south-central Idaho, reduced Wyoming big sagebrush from a prefire frequency of 100% to and average of 40% in postfire year 1. Wyoming big sagebrush seedlings had not recolonized by postfire year 3 [105].

Wyoming big sagebrush may be less able to benefit from the increased nutrient load on recently burned sites than associated grasses. In a greenhouse study, cheatgrass and bottlebrush squirreltail seedlings showed a significant increase (p = 0.05) in total biomass when grown on soil collected from a new burn compared to growth on soil from an adjacent unburned site. Biomass of Wyoming big sagebrush seedlings was slightly (but not significantly) less when grown on soil from the burn compared to biomass when grown on soil from the unburned site [17].

Plant Response to Fire

Wyoming big sagebrush is not an initial colonizer. It may be slow to establish on a burn, especially when compared to other big sagebrush subspecies, because of the relatively drier sites it normally occupies [21,24,27]. Additionally, the VAM upon which Wyoming big sagebrush depend for healthy growth are harmed by fire, and may take several years after fire to recover [71,109]. Wicklow-Howard [148] found that on the Snake River Birds of Prey Area of southern Idaho, fewer of the VAM associated with Wyoming big sagebrush were killed by low-intensity fire than by moderate-intensity fire.

In southwestern Montana, Wyoming big sagebrush seedlings were still absent from a prescribed burn site 6 years after fire [137]. In the Missouri River Breaks of central Montana, wildfire removed the Wyoming big sagebrush from a Wyoming big sagebrush/bluebunch wheatgrass community, and it was not found during vegetation sampling performed at postfire year 14. Total coverage at that time was 50% grasses, with the remainder consisting of forbs and bare ground. Shrub cover was "minimal" [43].

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Fire Ecology

Fire adaptations: Fire is the principal means of renewal for decadent stands of Wyoming big sagebrush [17]. Wyoming big sagebrush establishes after fire from the seedbank [12,90,112]; from seed produced by remnant plants that escaped fire [29]; and from plants adjacent to the burn that seed in [29,31]. Fires in Wyoming big sagebrush are usually not continuous, and remnant plants are the principal means of postfire reproduction [29]. Fire does not stimulate germination of soil-stored Wyoming big sagebrush seed, but neither does it inhibit its germination [30].

Litter production is lower in Wyoming big sagebrush communities than in other big sagebrush subspecies, but still may be greater than litter production in communities dominated by other cold-desert shrubs. In the Curlew Valley of northern Utah, average annual litter production was greater in Wyoming big sagebrush (192 g/m2/year) than in winterfat (Krascheninnikovia lanta) or shadscale (Atriplex confertifolia) communities [145].

FIRE REGIMES have been radically altered in Wyoming big sagebrush communities heavily invaded by cheatgrass [27,66,76,89,116,129]. Cheatgrass dominates many Wyoming big sagebrush stands in southern Idaho, northern Nevada, and eastern Oregon. Annual cheatgrass production is highly variable and can be considerable in years of favorable precipitation. An abundance of cheatgrass enhances the likelihood of fire spread [27]. Fire hazard is estimated to be 5 times as great in big sagebrush communities converted to cheatgrass [106]. Besides removing Wyoming big sagebrush, frequent fire may also inhibit its re-establishment. Repeated burning and invasion by cheatgrass removes VAM associated with Wyoming big sagebrush [109]. Some Wyoming big sagebrush sites in southern Idaho have burned 2 or 3 times within 10 years [18]. On such sites, Wyoming big sagebrush is not regenerating before the next fire cycle, and former steppes are converting to annual grasslands [97].

FIRE REGIMES in other types: Fire return intervals in communities in which Wyoming big sagebrush is an important component of the understory are similar to those of Wyoming big sagebrush communities and are summarized below. For further information on FIRE REGIMES in these forest and woodland communities, see the FEIS species report.

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Successional Status

Wyoming big sagebrush is a mid- to late-seral species [41,54,125]. Period of Wyoming big sagebrush establishment after a stand-replacing event such as fire is typically about a decade but varies with site [125]. Prior to re-establishment of Wyoming big sagebrush, disturbed Wyoming big sagebrush communities are mostly populated with associated grasses. Principal component analysis of Wyoming big sagebrush steppe on the Thunder Basin National Grassland of Wyoming produced this successional model (intervals between seres were not quantified) [13]:

Wyoming big sagebrush/cheatgrass associations are most common on frequently disturbed sites. In the Trout Creek Mountains of Oregon, the type occurs on floodplains with large amounts of bare ground cover [46].

Wyoming big sagebrush may lose dominance on some steppe that have not experienced fire or other stand-replacing events for half a century or more. Kindschy [81] noted that in pristine Wyoming big sagebrush/bluebunch wheatgrass on Oregon's Jordan Crater Natural Research Area, most sites with a preponderance of dead Wyoming big sagebrush were the oldest seres. Old seres were primarily populated with long-established perennial herbs, with a few decadent Wyoming big sagebrush.

VAM associated with Wyoming big sagebrush are killed by heating or chemical alteration of the soil, and they may take several years to recolonize after fire or other soil-altering disturbance [148]. Absence of VAM probably inhibits Wyoming big sagebrush establishment on disturbed soils. For example, 2.5 years after restoration work, VAM had not yet colonized a coal-mined site in south-central Wyoming even though stockpiled topsoil was replaced. When VAM-infected and noninfected Wyoming big sagebrush seedlings were transplanted on the site, there was no significant difference in growth between the 2 groups: both showed poor establishment. In the greenhouse, however, biomass gain of the infected group was significantly greater (about 1.5 times more, p=0.05) compared to the uninfected group. This suggests that on the disturbed site, VAM were unable to survive anywhere but inside Wyoming big sagebrush roots, and establishment of VAM and host Wyoming big sagebrush probably will not occur until the chemistry of lower soil horizons changes [122].

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Regeneration Processes

Wyoming big sagebrush reproduces from seed; it does not sprout or layer [12,90,112]. Pollination is mostly by outcrossing, but plants can also self pollinate [56]. Shrubs produce large quantities of small seeds beginning at 3 to 4 years of age [90,129]. Goodwin [60] estimated that a moderate-sized plant produces about 350,000 seeds in a season, and a large one produces over a million. Big sagebrush seed is disseminated mostly by wind, with some seed spread by animals and water [60,116]. The seed floats, so seedlings may establish along watercourses [60,98]. Most seed shatters within a week of maturation [60] and travels less than 100 feet (30 m) from the parent plant [10,129]. Some viable seed is retained on the parent and disseminates slowly over the winter [98]. Establishment occurs mostly from the seedbank [67]. Wyoming big sagebrush seed stored in the warehouse has retained viability for at least 6 years [116]; viability in the field is unknown. On burns, Wyoming big sagebrush that escape fire are an important seed source [29]. If the seedbank is destroyed over a large area by repeated fires or other means, Wyoming big sagebrush eventually seeds in from adjacent areas, but such a strategy may take several decades [129].

Seeds are nondormant, but a short (< 4 week) stratification period and light improve germination [92,93,98]. Germination rates in the laboratory are high over a broad range of temperatures (50-95 oF (10-35 oC)) [40,116]. Fresh seed collected over 5 western states showed germination rates of 69 to 100% [93]. Year-to-year seed viability seems more than adequate; germination rates of fresh seed collected in 3 successive years near Dubois, Idaho, ranged from 43 to 70% (mean=54%) [61].

A light litter layer favors seedling establishment; heavy litter retards establishment. Drought conditions favor establishment of Wyoming big sagebrush over perennial bunchgrasses [10]. Seedling growth is slow compared to growth of other subspecies and is probably under genetic control. Wyoming big sagebrush seedlings grow slowly even when water and nutrients are not limiting [17,20]. In the greenhouse, well-watered Wyoming big sagebrush seedlings stopped growth earlier in the growing season and attained less height than mountain and basin big sagebrush seedlings. Under drought conditions, Wyoming big sagebrush seedlings were not only shorter in stature, but also had smaller aboveground parts, than the other 2 major subspecies [20]. Seedling mortality can be high under drought conditions [40]

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Life History and Behavior

Cyclicity

Phenology

Wyoming big sagebrush develops ephemeral leaves in early spring and retains them until onset of summer drought. Perennial leaves develop slowly, from late spring until July. Perennial leaves are generally retained until their 2nd year, when they are shed during summer drought. By retaining about 1/3rd of its perennial leaves over winter and then developing ephemeral leaves early in the growing season, Wyoming big sagebrush begins photosynthesis and height growth earlier than most herbaceous associates [38,96]. Relatively more leaves are shed in dry years compared to wet ones, and new leaves tend to be smaller in dry years [85]. Flowering begins in late summer (Aug. or Sept.), and fruits ripen in fall (mid-Oct. to mid-Nov.) [116,149]. Flowering continues until the onset of cold weather. Most seed is shed in fall, but some seed shed may continue until early winter [98].

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Threats

Pests and potential problems

Perhaps the greatest danger to sagebrush stands comes from fire. Big sagebrush plants have no fire resistance and many acres are destroyed annually because of increased fire frequency resulting from infestations of exotic annual weeds such as cheatgrass and medusahead.

Another minor cause of sagebrush mortality is winter injury. This occurs when temperatures drop quickly below freezing before plants have entered dormancy, or when a warm spell promotes winter growth followed by a return to typical winter temperatures. Extended periods of winter and summer drought (normally more than 2 years) can also cause dehydration and death.

Big sagebrush is occasionally susceptible to limited outbreaks of the sagebrush defoliator moth, or webworm, (Aroga websteri). Although the moths can cause extensive damage, they too are subject to insect predators, and it is rare that entire stands will be lost.

Additionally, there are a number of other microbial and fungal pathogens known to attack big sagebrush. Although these may inflict serious damage locally, they have not been viewed as a great threat to sagebrush populations.

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Management

Management considerations

Grazing: Wyoming big sagebrush normally appears in mid-seral steppes, and good grazing management will not prevent its reinvasion [62]. It may increase moderately under heavy grazing; however, because of its relatively high palatability it does not increase as much as other big sagebrush subspecies usually do [112,131]. Schlatterer [113] reported that in northern Idaho, Wyoming big sagebrush increased slightly with overgrazing. On some overgrazed sites, Wyoming big sagebrush has declined nearly as much as associated bunchgrasses, and its coverage has actually increased with cessation of grazing. On the Upper Snake River Plains of southeastern Idaho, Wyoming big sagebrush and associated bunchgrasses were depressed from approximately 50 years of heavy domestic sheep and cattle grazing. When grazing was stopped in 1950, Wyoming big sagebrush cover increased significantly (p=0.05), from 15% in 1950 to 22% by 1965 [3].

Total productivity in Wyoming big sagebrush communities is low, from less than 400 lbs/acre (450 kg/ha) on poor sites to 900 lbs/acre (1013 kg/ha) on the most productive sites [112].

Control: Wyoming big sagebrush can be controlled by burning or with herbicides. Because Wyoming big sagebrush provides palatable browse for livestock and big game animals, even on poor soils, Beetle and Johnson [11] recommend caution when reducing it. Among control methods, fire is the most effective [8,32,137,138] (see Fire Effects). It is also the least expensive [138]. Bastian and others [8] present an economic threshold analysis integrating cost-effectiveness of fire or 2,4-D control on Wyoming big sagebrush rangelands, projected over 15 to 25 years, with breakeven return per AUM. Their model predicts that chemical control is generally about twice as costly as fire control.

Phenoxy herbicides generally control Wyoming big sagebrush [4,32,79,85,137]. In central Nevada, 2,4-D caused a 75% reduction in Wyoming big sagebrush [32]. Winter or early spring spraying reduces Wyoming big sagebrush at a time when most herbaceous species are dormant and less harmed by herbicides [4].

2,4-D does not effectively control Wyoming big sagebrush in New Mexico (35-50% mortality) [6,91]. Teuthiuron application resulted in 80% mortality of Wyoming big sagebrush in northern New Mexico [6].

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Cultivars, improved and selected materials (and area of origin)

‘Hobble Creek’ mountain big sagebrush was released by the Utah Agricultural Experiment Station, Utah State University and the USDA Forest Service Rocky Mountain Research Station in 1987. Seed was originally collected in 1968 by A. Perry Plummer at the Hobble Creek drainage east of Springville, UT. ‘Hobble Creek’ was chosen for its high vegetative production and for its high palatability to mule deer and wintering domestic sheep. It is adapted to sites with deep, well-drained soils receiving more than 350 mm (14 in) of annual precipitation and having a growing season of 90 days or longer. Soils should be no finer than a clay loam, containing 40% or less clay and have a pH between 6.6 and 8.6. Breeder seed is maintained at a breeder block at the USDA Forest Service Rocky Mountain Research Station, Shrub Sciences Laboratory, Provo, UT.

‘Gordon Creek’ Wyoming big sagebrush was originally collected near Helper, Carbon County, UT. It was released in 1992 by the USDA Forest Service Rocky Mountain Research Station to fill the need for a low precipitation ecotype of big sagebrush to improve winter diets of mule deer and sage grouse and for rangeland restoration. Gordon Creek was chosen for its high growth rate, nutrient levels and mule deer preference. It is widely adapted to dry regions of the west receiving 250 or more mm (10 in) mean annual precipitation. It prefers deep to shallow, well-drained soils with up to 55% clay content with a pH of 6.6 to 8.8.

Contact your local Natural Resources Conservation Service (formerly Soil Conservation Service) office for more information. Look in the phone book under ”United States Government.” The Natural Resources Conservation Service will be listed under the subheading “Department of Agriculture.”

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Seed production

The vast majority of big sagebrush seed used in revegetation is wildland collected material. Seed collection occurs in late fall to early winter (early October through the end of December) depending on the subspecies. Collections are commonly made by hand stripping, beating or clipping seed heads into containers or by using a reel type harvester. Seed can be cleaned with a hammermill, debearder, air-screen or gravity table with varying results. Most sagebrush seed lots used for rangeland seeding are only cleaned to a purity of 15 to 20 percent due to the small nature of the seeds (achenes). This practice requires less time for cleaning and also allows for easier seed flow and metering in seeding equipment. Pure seed yields approximately 1.7 to 2.5 million seeds per pound. The NRCS Plant Materials Center in Bridger, MT reported four hours collecting time and 5.5 hours cleaning yielded 200g (0.45 lb) cleaned material, or 21g (0.04 lb) per hour.

Sagebrush seed that has been dried to a minimum of 9 percent moisture content will remain viable for many years when stored under cool, dry conditions. Welch et al (1996) reported seed viabilities above 90% for seed stored at 10 ºC (50 ºF) and relative humidity (RH) of 20 percent after nine years of storage. Seed stored at higher RH levels are susceptible to germination or damage by insects or microorganisms.

Because sagebrush seed can readily be collected from wild stands, sagebrush is rarely grown in commercial production fields. However, in very droughty periods, very little sagebrush seed can be collected from wild stands. Increasing seed demands and decreasing sagebrush stands lost to weeds and fire are growing concerns. Recent studies suggest protecting wildland seed-producing stands for optimum harvesting. The greatest factor in seed production for sagebrush is protection against grazing animals. Surrounding plants with a wire fence has shown an increase in seed stalk number of as much as 3 to 5 times the amount of unprotected plants. Studies also show significantly higher seed yields from plants grown on reclaimed mine lands when compared with those on adjacent non-mined areas. The reason for this correlation is unclear, but it may be a result of increased available soil moisture due to lower competing plant frequencies on the mined lands.

Seed production varies greatly between years and between stands due to differences in climate, stand density and maturity, soil and genetics. It has been estimated that an average stand of big sagebrush could potentially produce 100 to 300 lbs PLS per acre annually. Seed production declines as plants and stands mature creating larger amounts of woody biomass. Greater seed yields can be achieved by thinning decadent stands to encourage new flower stalk production

For nursery plantings, pre-stratified seed can be planted in greenhouse conditions, or seed can be allowed to naturally stratify after being planted in containers outdoors. Keep soil medium slightly moist during germination. Greenhouse sprayers or misters are commonly used during daylight hours at a rate of 10 seconds every 15 minutes. Uniform germination occurs after two weeks of temperatures over 20º C (70º F). Seedlings are ready for field transplanting approximately 5 months after germination.

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Historically, sagebrush communities have been poorly managed, mostly in attempts to reduce or eliminate sagebrush stands to increase forage production for livestock. Recently, however, the value of sagebrush to the western rangelands is being recognized, and practices are evolving to better manage healthy and productive sagebrush communities.

Contrary to long standing beliefs, studies show that complete sagebrush removal negatively affects biodiversity and has little long term affect on perennial grass production. Indeed, several studies indicate that forage production may actually decline when sagebrush is completely removed or controlled.

Overgrazing of the understory decreases plant biodiversity, especially the forb component of the plant community and increases the density of weeds. Annual weeds, such as cheatgrass (Bromus tectorum L.) and medusahead (Taeniatherum caput-medusae [L.] Nevski) often out-compete young sagebrush seedlings and create undesirable monocultures. Annual weed infestations also increase the frequency of wildfires which result in eliminating sagebrush stands therefore not allowing stand re-establishment.

Despite the many valuable benefits of sagebrush to rangelands, there may be cases when it is desirable to thin and rejuvenate sagebrush stands. In these instances it is not necessary to remove the entire stand, and control treatments in mosaic patterns are recommended. Several methods exist for partial removal of the shrubby over story.

Herbicide use is an effective means of thinning sagebrush stands. Contact your local agricultural extension specialist or county weed specialist to determine what works best in your area and how to use it safely.

Probably the simplest and most cost effective means of stand reduction is through prescribed burning. If there is sufficient fuel, a burn can completely eliminate a sagebrush community. For this reason niche burning is recommended when possible. In situations where cheatgrass is a dominant part of the understory, burning should take place when ripe cheatgrass seeds are still on the plants and will be consumed in the fire.

Methods of mechanical removal for sagebrush include anchor chaining, pipe harrowing, land imprinting offset disking and brush beating with brush hogs or mowers. Of these, chaining and land imprinting are the least expensive and do an excellent job of reducing sagebrush stands while still leaving enough plants for diversity and browsing. Brush beating does a good job, but it is expensive. Disking and harrowing also do a good job of shrub removal, but are more expensive and more destructive to under-story plant populations.

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Relevance to Humans and Ecosystems

Benefits

Value for rehabilitation of disturbed sites

Wyoming big sagebrush is used for stabilizing slopes and gullies and for restoring degraded wildlife habitat, rangelands, mine spoils, and other disturbed sites [90,116]. It is particularly recommended on dry upland sites where other shrubs are difficult to establish [94]. It can be established by direct seeding [94,116] and by transplanting greenhouse seedlings or wildings. Wild plants are best moved while dormant in winter [90,119]. Commercial seed is available [35].

Wyoming big sagebrush has been recommended for seeding on coal-mined lands based upon tolerance of germinants to droughty and saline soils [41].

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Cover Value

Wyoming big sagebrush provides cover for a variety of wildlife including pronghorn [126,130], bighorn sheep [83], lagomorphs [80,140], shrub-nesting birds, and some ground-nesting birds including sage grouse [71,80]. Cover of mature shrubs is especially important to pronghorn fawns and sage grouse brood [80,130]. Early to mid-seral communities are important black-tailed jackrabbit and pygmy rabbit habitats [80,88,140]. In contrast, Townsend's ground squirrels, and raptors that rely on them as prey species, prefer open and grassy, early seral Wyoming big sagebrush communities such as burns. Their numbers decline as plant succession advances [80].

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Nutritional Value

Wyoming big sagebrush contains volatile oils, but is otherwise a highly nutritious shrub. The leaves equal alfalfa (Medicago sativa) in protein content, with slightly more carbohydrates and 12 times more lipids. Mule deer apparently avoid some of the effects of the volatile compounds by belching the compounds as they chew their cuds [98].

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Importance to Livestock and Wildlife

Wyoming big sagebrush is preferred browse for wild ungulates [22,105,116,141], and Wyoming big sagebrush communities are important winter ranges for big game [67,90,99,131]. Pronghorn usually browse Wyoming big sagebrush heavily [2]. On the Idaho National Engineering Laboratory, for example, the shrub comprised 90% of the diet of pronghorn from fall through spring. Lagomorphs may browse Wyoming big sagebrush heavily in winter [58]. Wyoming big sagebrush is a crucial food item of sage grouse, and Wyoming big sagebrush communities are critical habitat for the birds [4,31,52,53,131,143].

Livestock browse Wyoming big sagebrush, but may use it only lightly when palatable herbaceous species are available [102,117]. In south-central Wyoming, Wyoming big sagebrush formed about 10% of the spring and summer diet of domestic sheep. Cattle use was negligible. In contrast, it formed 85% of the spring diet of pronghorn on the same range [102]. In a Gambel oak (Quercus gambelii) community in northern Utah, domestic goats preferred almost any other browse to Wyoming big sagebrush [108].

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Other uses and values

Native Americans made tea from big sagebrush leaves. They used the tea as a tonic, an antiseptic, for treating colds, diarrhea, and sore eyes, and as a rinse to ward off ticks. Big sagebrush seeds were eaten raw or made into meal [98]. The wood is extremely aromatic when burned, and the wood smoke was used to mask the effects of an encounter with a skunk [45].

Big sagebrush was little used by European-American settlers. They occasionally used the branches for thatching [135]. The wood produces a very hot fire, and was used in mine smelters [98].

Big sagebrush has little current commercial use. It is sometimes used for xeriscaping [64,98].

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Palatability

Wyoming big sagebrush is generally the most palatable of the big sagebrush subspecies, and big game species use it heavily, especially in winter [112,131]. In a trial using captive mule deer, it was the most preferred among the 3 major subspecies of big sagebrush [22]. It is moderately palatable to cattle and domestic sheep [131].

Coumarin, a compound present in big sagebrush leaves, imparts a bitter taste that affects animal use. There are regional differences in ungulate use of Wyoming big sagebrush relative to other big sagebrush subspecies, which may be at least partially due to between-population differences in coumarin concentration in Wyoming big sagebrush leaves [136,141]. For example, domestic sheep on the Kaibab Plateau of Arizona preferred Wyoming big sagebrush over either mountain or basin big sagebrush. Mule deer selected Wyoming big sagebrush as their 2nd choice among the 3 subspecies, but preferred mountain big sagebrush [142]. In eastern Oregon, however, Wyoming big sagebrush was the least palatable of 7 sagebrush taxa to domestic sheep but was moderately palatable to mule deer [117].

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Uses

Forage/Wildlife: Big sagebrush is perhaps the most important shrub on western rangelands. Evergreen leaves and abundant seed production provide an excellent winter food source to numerous species of large mammals including mule deer, black-tailed deer, white-tailed deer, elk, pronghorn antelope, bighorn sheep and jack rabbits. Nearly 100 bird species depend on sagebrush ecosystems for their habitat needs. Additionally, there are several animal species having an obligate relationship with big sagebrush including sage grouse, sharp tailed grouse, pygmy rabbits, sage thrashers, sage sparrows and Brewer’s sparrow. Sagebrush also provide habitat and food for hosts of invertebrates which in turn support birds, reptiles and small mammals. In addition to the numerous species of animals that depend on sagebrush for food and cover, there are several plant species having close relationships with sagebrush as well.

Sagebrush plants maintain high levels of most nutrients including crude protein (see table 1). This high forage value makes it especially useful for wildlife, and in some areas livestock, winter grazing. Separate studies indicated that sagebrush made up 78% of the annual diet for antelope in Wyoming and 59% of the winter diet of deer and elk near Gardiner, Montana. Sagebrush also makes up close to 100% of the winter diet of sage grouse and over 60% of their total annual diet. Use of sagebrush by livestock is limited and variable.

Animal preference of sagebrush varies with subspecies, populations and even individual plants due to chemical variation found in the foliage. Deer and elk tend to prefer mountain big sagebrush followed by Wyoming big sagebrush and finally basin big sagebrush. Although many range managers believe that deer and other large mammals prefer to browse shrubby members of the Rosaceae such as mountain mahogany (Cercocarpus), bitterbrush (Purshia) and cliffrose (Cowania) over big sagebrush, studies show sagebrush significantly more readily browsed.

Sagebrush’s value as thermal or security cover is also very high for wildlife. This includes nesting cover and escape cover for sage grouse, sharp tailed grouse, pheasants, chukar and other upland birds.

Revegetation/reclamation: Because of its wide range of adaptation and ease of establishment, big sagebrush can be a very important species for use in revegetation efforts. Seedlings are able to compete with grasses and forbs as well as other shrubs allowing it to be used as a component of a wide range of seed mixes. Seedlings are very easy to establish when planted correctly (see “Establishment” section) and can be drill seeded or broadcast with near equal levels of success. Because sagebrush plants spread readily by seed, it can be seeded at relatively low rates and allowed to spread by natural recruitment.

Big sagebrush plants provide many additional benefits to the plant community. The dense canopy protects understory herbaceous plants from grazing. Healthy sagebrush communities provide a multi- tiered ecosystem with high levels of biodiversity. Big sagebrush plants also have a two-part root system with a deep tap root and a shallow, diffuse root system. Numerous studies have shown sagebrush plants create “hydraulic lift” where deep soil moisture is brought to near the soil surface by the tap root system during the day and then released into the upper soil at night. This water is then available to the diffuse root system of big sagebrush as well as to the roots of other understory plants. Sagebrush plants also increase water retention by trapping and holding windblown snow.

Big sagebrush subspecies are often useful indicators of soil characteristics. Generally, a subspecies indicates the soils at a site, thus proper identification of big sagebrush at a subspecific level can provide useful information on soils and ecological site characteristics. In some areas, however, such as those with glacial deposits, a separation based on soil characteristics is considerably more complex.

Besides the 3 major subspecies mentioned above, at least 2 other subspecies of big sagebrush with limited distributions are recognized: A. t. subsp. parishii [64] and A. t. subsp. xericensis [77]. Snowfield big sagebrush has been classified both within in the big sagebrush complex (A. t. subsp. spiciformis) [59,77] and as a distinct species (A. spiciformis) [64].

In this report, the name "big sagebrush" is used when discussing the big sagebrush species complex. Infrataxa including Wyoming big sagebrush are referred to by the subspecific common names used above.